Imposing categories on dimensions

  The range of human variation is something we cherish. We would hate a world where everyone had the same personality, where there were no sensitive individuals, no moody individuals, no brave brash ones, etc. Similarly life without emotional variation would be intolerable. Aldous Huxley’s book Brave New World (where everyone was able to remain constantly content by taking a drug called ‘Soma’) was a nightmare scenario, not a utopia. Normal

  Diagnostic Criteria for Major Depressive Episode (DSM IV*)

  Five (or more) of the following present during the same 2 week period and is a change from previous functioning; at least one of the symptoms is either (1) depressed mood or (2) loss of interest or pleasure.

  Depressed mood most of the day, nearly every day (e.g. feels sad or empty) or observed by others (e.g. appears tearful).

  Markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day (subjective account or observation).

  Significant weight loss or weight gain (more than 5% of body weight in a month), or decrease or increase in appetite nearly every day.

  Insomnia or hypersomnia nearly every day.

  Agitation or retardation nearly every day (observable by others).

  Fatigue or loss of energy nearly every day.

  Feelings of worthlessness or excessive or inappropriate guilt nearly every day.

  Diminished ability to think or concentrate, or indecisiveness, nearly every day.

  Recurrent thoughts of death, recurrent suicidal ideation. The symptoms do not meet criteria for a Mixed Episode.

  The symptoms cause clinically significant distress or impairment in social or occupational functioning.

  The symptoms not due to drug abuse, medication, or a general medical condition.

  The symptoms are not better accounted for by bereavement.

  *DSM IV = the fourth version of the Diagnostic and Statistical Manual produced by the American Psychiatric Association. A codification of diagnostic criteria for psychiatric disorders used worldwide. ‘Statistical’ refers to the use of these categories to record diagnoses and treatment.

  intensities of sadness (e.g. in grief) or fear (e.g. in a house fire) match anything to be found in mental illnesses. There is no consistent cut-off, no absolute distinction between the normal and the abnormal – it is not a simple matter of degree. Even hearing voices when there is nobody about (auditory hallucinations) occurs in ‘normal’ people. Research in the Netherlands found a significant number of healthy people who regularly ‘hear voices’; widows and widowers regularly hear the voice of their dead partner quite clearly (and usually find it comforting). So how can the psychiatrist claim that hallucinations are symptoms of mental illness?

  Medical practice involves pattern recognition. For most disorders there is a set of symptoms and signs that characterize it. Not all have to be present to make the diagnosis, although obviously that makes it easier. If some of the symptoms are very prominent then we hardly need to confirm the others, but if none is very striking we will seek to complete the picture. The intensity and duration of the symptoms also matter (how long the anxiety lasts, how persistent and disruptive the voices). Judgements must accommodate cultural differences. Northern Europeans are usually much less emotionally demonstrative than Southern Europeans so the thresholds for concern about expressions of distress may vary, for example, between a Finn and an Italian.

  Traditionally medical training involved seeing as many patients as possible to learn these patterns within the normal range of expression. More recently diagnostic systems have become more formalized, often requiring some features absolutely and then a selection of others as shown in the current diagnostic criteria for depression. This has certainly improved consistency but the process is still the same. In this example ‘lowered mood’ is treated as a yes/no, present/absent quality, when we all know that mood varies continuously between people and over time. Psychiatric diagnoses require the imposition of categories (yes/no, present/absent) onto what are really dimensions (a little/quite a bit/a bit more/quite a lot/too much).

  This is very obvious in psychiatry but it is certainly not unique to it. Our popular view of illnesses is usually based on the examples of infectious diseases or surgical trauma – you ’ve either got an infection or you have not, your leg is either broken or it is not. There is no ambiguity and no need for agreement or consensus. However, few illnesses are that straightforward. Even the infection example is not that simple – you can find the same bacteria that cause pneumonia in lots of perfectly healthy people. The diagnosis is not made just by finding the bacteria but by finding them in the presence of a fever and cough. Even objective, verifiable data don’t always resolve the issue. What is considered ‘pathological’ will change depending on changing knowledge about diseases and available treatments. Just as improved treatments have led us to lower the threshold for depression so the diagnosis of disorders as apparently concrete and measurable as diabetes and high blood pressure is constantly redefined.

  So psychiatry is not for the faint-hearted or those who need too much intellectual security. It is, of all the branches of medicine, the one that most clearly exposes the processes behind making a diagnosis. The language is revealing – doctors ‘make’ diagnoses, they impose their patterns rather than simply discovering them. It is also the branch of medicine which most explicitly acknowledges the impact of social considerations on its practice. Both the definitions of disorders used by psychiatrists and their expression in individuals are moulded by the social context. For example, modern society identifies and treats battle stress or shell-shock in war as a psychiatric disorder whereas a century ago we punished it as cowardice. Young adults at the start of the 21st century will seek help for their problems in a manner utterly unrecognizable to how their stoical grandparents would have done. This doesn’t make psychiatry particularly unscientific or unreliable (psychiatric diagnoses are about as reliable as those in medicine overall). However, it reminds us that, like medicine, it remains (despite current wishful thinking) both an art and a science and draws from both social and physical sciences.